The effects of phosphate fertilizer on growth, yield and anthracnose resistance in chili (Capsicum annum) plant

Abstract

Chili plants (Capsicum annum) are globally cultivated for their culinary, economic, and medicinal value, with their diverse flavors and spiciness enriching cuisines worldwide. In Sri Lanka, chili is a key condiment and an important cash crop. However, production falls short of annual demand due to various factors, notably anthracnose, a group of fungal disease caused by Colletotrichum fungi, leading to significant crop yield losses. Therefore, this study examined the effects of different levels and forms of phosphate fertilizer on chili plant growth, yield, and disease resistance, particularly against anthracnose disease. The experiment was conducted in the wet zone, spanning September to December. Data collection occurred from October to December (2023). The MICH HY1 chili variety was selected for this research based on its high potential yield of 32 t/ha, adaptability to major chili-growing regions in Sri Lanka and moderate resistance to Leaf Curl disease of Chili (LCDC). Plants were treated with three different levels of Triple Super Phosphate (TSP); 0.5g, 1.0g, and 1.5g in two forms along with 0.0022g/mL Albert’s solution per plant, and control was maintained without phosphate treatment, weekly for six weeks, under greenhouse conditions in grow bags (13×13cm2). The experiment was set up in a Randomized Complete Block Design (RCBD) with four experimental units per treatment. The growth and yield were assessed using five parameters: plant height, leaf count, leaf area, days to 50% flowering, and the number of fruits per plant. Colletotrichum was isolated from infected chili samples and morphologically identified. Chili leaves were exposed to isolated Colletotrichum under in-vitro conditions and lesion areas were measured using ImageJ software V1.8.0. Findings revealed the highest fruit yield with an average of 13 fruits per plant under the treatment of 1.0g of powdered phosphate fertilizer suggesting it as the suitable level to maximize yield. Conversely, the smallest lesion area of 1.258cm2, indicating the highest resistance to anthracnose, was recorded with the application of 0.5g phosphate in powdered form, suggesting that level to be used to enhance resistance to anthracnose disease. Additionally, the results revealed that excessive phosphate application led to stunted growth and increased susceptibility to anthracnose disease.